S-93C46C Datasheet, PDF (23/39 Pages) Seiko Instruments Inc – 3-WIRE SERIAL E2PROM

Rev.1.1_00
3-WIRE SERIAL E²PROM
S-93C46C/56C/66C/76C/86C
 3-Wire Interface (Direct Connection between DI Pin and DO Pin)
There are two types of serial interface configurations: a 4-wire interface configured using the CS pin, the SK pin, the DI
pin and the DO pin and a 3-wire interface that connects the DI pin and the DO pin.
When the 3-wire interface is employed, a period in which the data output from the CPU and the data output from the
serial memory collide may occur, causing a malfunction. To prevent such a malfunction, connect the DI pin and the DO
pin of this IC via a resistor (10 kΩ to 100 kΩ) so that the data output from the CPU takes precedence in being input to
the DI pin (refer to Figure 22).
CPU
S-93C46C/56C/66C/76C/86C
SIO
DI
DO
R: 10 kΩ to 100 kΩ
Figure 22 Connection of 3-Wire Interface
 Input Pin and Output Pin
1. Connection of input pin
All input pins in this IC have the CMOS structure. Do not set these pins in "High-Z" during operation when you design.
Especially, set the CS pin to "L" at power-on, power-off, and during standby. The error write does not occur as long as
the CS pin is "L". Set the CS pin to GND via a resistor (the pull-down resistor of 10 kΩ to 100 kΩ).
To prevent the error for sure, it is recommended to use equivalent pull-down resistors for input pins other than the CS
pin.
2. Equivalent circuit of input pin and output pin
Figure 23, Figure 24 and Figure 25 show the equivalent circuits of input pins in this IC. In Figure 23 and Figure 24,
none of the input pins incorporate pull-up and pull-down elements, so special care must be taken when designing to
prevent a floating status.
In Figure 25, the TEST pin has a built-in pull-down element.
Figure 26 shows the equivalent circuit of the output pin. This pin has the tri-state output of "H" / "L" / "High-Z".
23